Map display device and map display system

ABSTRACT

A map display device includes: a processor that defines a coordinate system on a map including element polygons showing constituent elements of an urban map; a processor that sets coordinates located inside the element polygons as inner coordinates and sets coordinates located outside the element polygons as outer coordinates; a processor that calculates, for each coordinate in the coordinate system, a moving average value; a processor that resets each of the outer coordinates which has the moving average value larger than a predetermined value as the inner coordinate; a processor that sets, as an urban polygon, a polygon along an outer periphery of a region formed of an aggregate of the set and reset inner coordinates; and a processor that enables the urban map to be displayed when a current location is present inside the urban polygon.

CROSS REFERENCE TO RELATED APPLICATION

The present disclosure is a U.S. national stage application ofInternational Patent Application No. PCT/JP2013/005999 filed on Oct. 8,2013 and is based on Japanese Patent Application No. 2012-258498 filedon Nov. 27, 2012, the disclosure of which is incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a map display device and a map displaysystem.

BACKGROUND

For example, Patent Literature 1 discloses a navigation apparatus, whichis mounted in a vehicle (referred to as a host vehicle) and sets in mapdata a polygon that encloses a region where an urban map is present. Theurban map is enabled to be displayed when the location (host vehiclelocation) of the host vehicle is present inside the polygon region; incontrast, the urban map is disabled from being displayed when the hostvehicle location is present outside the polygon region. Such an urbanmap can be referred to also as street directory and includes buildingsand sites facing streets as constituent elements.

PATENT LITERATURE

Patent Literature 1: JP 2000-337894 A

The polygon (hereinafter referred to as an “urban polygon”) enclosingthe region where the urban map is present needs to be updated in such acase as when map data is organized and the urban map is newly edited. Ifsuch an updating process is manually performed by the producer of themap data or the user of the navigation apparatus, enormous labor isrequired and, in addition, a human error is likely to occur.

SUMMARY

It is an object of the present disclosure to provide a map displaydevice and a map display system which enable an urban polygon to beautomatically updated with high precision without depending on humanmanipulation.

A map display apparatus and a map display system according to an aspectof the present disclosure each are provided as follows. A coordinatesystem is defined on a map including element polygons showingconstituent elements of an urban map. Coordinates located inside theelement polygons are set as inner coordinates; coordinates locatedoutside the element polygons are set as outer coordinates. For eachcoordinate in the coordinate system, a moving average value iscalculated by using a predetermined window width. Each of the outercoordinates which has the moving average value larger than apredetermined value is reset as the inner coordinate. A polygon is setas an urban polygon to be along an outer periphery of a region formed ofan aggregate of the inner coordinates that have been set and the innercoordinate that has been reset. The urban map is enabled to be displayedwhen a current location is present inside the urban polygon.

That is, the above-described map display device and the map displaysystem each permit an urban polygon to be automatically set on the basisof an aggregated region formed of an aggregate of the inner coordinatesset inside the element polygons and the inner coordinates resulting fromconversion of outer coordinates based on moving average values. Inaddition, since the aggregated region formed of the aggregate of theinner coordinates includes the element polygons corresponding to theconstituent elements of an urban map, a high-precision urban polygonadequate to the configuration of the urban map can be set on the basisof the aggregated region. This enables to automatically update the urbanpolygon with high precision without depending on human manipulation.

BRIEF DESCRIPTION OF DRAWINGS

The above and other objects, features and advantages of the presentdisclosure will become more apparent from the following detaileddescription made with reference to the accompanying drawings. In thedrawings:

FIG. 1 is a functional block diagram schematically showing aconfiguration of a navigation apparatus according to a first embodiment;

FIG. 2 is a view visually showing map data including element polygonsshowing constituent elements of an urban map;

FIG. 3 is a view visually showing a state where a coordinate system isdefined on a map;

FIG. 4 is a view visually showing a state where inner coordinates andouter coordinates are set in the coordinate system;

FIG. 5 is a diagram showing examples of expressions for calculating amoving average value;

FIG. 6 is a view visually showing a state where any one of outercoordinates which has a moving average value larger than a predeterminedvalue is reset as an inner coordinate;

FIG. 7 is a view visually showing a state where the outer coordinatesurrounded by the inner coordinates is reset as an inner coordinate;

FIG. 8 is a view visually showing a state where the inner coordinateincluded in a region smaller than a predetermined area is reset as anouter coordinate;

FIG. 9 is a view visually showing a state where the inner region isreduced by dimensions each corresponding to the maximum value of roadwidths;

FIG. 10 is a view visually showing a state where a polygon along theouter periphery of the inner region is set as an urban polygon;

FIG. 11 is a view showing a state where a host vehicle location ispresent inside the urban polygon;

FIG. 12 is a view showing a state where an urban map is displayed on adisplay unit;

FIG. 13 is a flowchart illustrating an urban polygon automatic settingprocess;

FIG. 14 is a flowchart illustrating an urban-map display/non-displaysetting process; and

FIG. 15 is a functional block diagram schematically showing aconfiguration of a map display system according to a second embodiment.

DETAILED DESCRIPTION

The following will describe the plurality of embodiments of the presentdisclosure with reference to the drawings. Note that components whichare substantially the same in each of the embodiments are designated bythe same reference numerals and a description thereof is omitted.

First Embodiment

A navigation apparatus 10 shown in FIG. 1 corresponds to a map displaydevice which displays a map on the basis of map data. The navigationapparatus 10 includes a control unit 11, a location measurement unit 12,a manipulation unit 13, a storage unit 14, a display unit 15, and anavigating unit 16. The control unit 11 is referred to also as a controlcircuit 11 and formed mainly of a microcomputer having a CPU, a ROM, ora RAM unshown to control the general operation of the navigationapparatus 10. The control unit 11 also executes a control program in theCPU to virtually implement a coordinate system definition processor 21,an inner and outer coordinate setting processor 22, a moving averagecalculation processor 23, an inner coordinate resetting processor 24, anouter coordinate resetting processor 25, an urban polygon settingprocessor 26, and an urban map display processor 27 using software. Notethat these processors 21 to 27 may also be implemented as an integratedcircuit integral with the control unit 11 using hardware.

The location measurement unit 12 measures the current location of avehicle (referred to as a host vehicle or a subject vehicle) in whichthe navigation apparatus 10 is mounted, i.e., a host vehicle location,and outputs locational information showing the measured host vehiclelocation to the control unit 11. The location measurement unit 12includes various detection means such as an azimuth sensor 121, a gyrosensor 122, a distance sensor 123, and a satellite wave receiver 124.The azimuth sensor 121 detects the azimuth of the vehicle. The gyrosensor 122 detects the rotation angle of the vehicle. The distancesensor 123 detects the running distance of the vehicle. The satellitewave receiver 124 receives the electric wave transmitted from apositioning satellite unshown so as to measure the current location ofthe vehicle using a positioning system. The location measurement unit 12measures the host vehicle location on the basis of detection values fromthe azimuth sensor 121, the gyro sensor 122, the distance sensor 123,and the satellite wave receiver 124.

The manipulation unit 13 includes a mechanical switch provided in thevicinity of the screen of the display unit 15 and the touch panel switchprovided on the screen of the display unit 15. The user uses each of theswitches of the manipulation unit 13 to input various commands forperforming, e.g., the setting of a destination in route guidance, theswitching of the configuration of the display screen of the display unit15 or the display output mode, the changing of the reduction rate of amap to be displayed, the selection of a menu screen, the retrieval of aroute, the initiation of the rooting guidance, the correction of acurrent location, and the adjustment of a sound volume. The navigationapparatus 10 operates on the basis of the input command.

The storage unit 14 is formed of a storage medium such as a detachableflash memory card or a hard disk drive. The storage unit 14 storesvarious data such as map data and information to be updatable. The mapdata includes various data such as road data formed of a plurality ofnodes forming roads and links connecting the individual nodes,coordinate data showing a location on the map, map matching data forassigning the host vehicle location onto a road, table data forreflecting traffic information on road data, and other data includingbackground data, land mark data, and destination data.

As shown in FIG. 2, the map data is divided into a plurality ofcompartments as shown by the broken lines a and includes elementpolygons P (element polygon data) showing the constituent elements ofthe urban map. The urban map can be referred to also as street directoryand has buildings and sites facing streets as the constituent elements.Examples of the element polygons P serving as the constituent elementsforming the urban map include a building polygon Pa showing a building,a site polygon Pb showing a site, a park polygon Pc showing a park, anda green space polygon Pd showing a green space. The element polygons Pare designed to be updated to those showing a latest urban mapconfiguration as a result of the updating of the map data on the basisof data distributed from, e.g., a map data distribution server notshown. Note that the constituent polygons P are not set to the portionscorresponding to the roads D and vacant spaces L each included in theurban map, i.e., portions having no constituent element.

The map data also includes an urban polygon PS (urban polygon data) as apolygon enclosing the region where the urban map including the pluralityof element polygons P is present. The urban polygon PS can automaticallybe updated, i.e., reset by an urban polygon automatic setting processdescribed later in detail. Note that the urban polygon PS shown in FIG.2 includes regions Aα and Aβ where the element polygons P are notpresent; namely, regions Aα and Aβ should not be included in the urbanmap to be displayed. The region Aα is a region where no element polygonis present in the compartment in which data on the urban map isprepared. The region Aβ is a region where no element polygon is presentin the compartment in which data on the urban map is not prepared. Thenavigation apparatus 10 performs an urban map display process when thehost vehicle location is present inside the urban polygon. Such an urbanpolygon PS thus causes the urban map display process to be undesirablyperformed even when the host vehicle location is present in the regionAα or Aα that is placed outside an urban area.

The display unit 15 is formed of, e.g., a liquid crystal or organic ELcolor display. On the screen of the display unit 15, a map of thesurroundings of the host vehicle location can be displayed at variousreduction rates on the basis of the map data. Also, on the screen of thedisplay unit 15, a current location mark M (see FIG. 11) showing thehost vehicle location and the direction of travel of the vehicle isdisplayed to be superimposed on the displayed map. In the case ofperforming route guidance to a destination, a screen for route guidanceis displayed on the screen of the display unit 15. Also, on the screenof the display unit 15, as will be described later in detail, an urbanmap G (see FIG. 12) can be displayed on the basis of the elementpolygons P.

The navigating unit 16 includes a guidance route retrieving processorwhich retrieves a guidance route for the vehicle and a map data readingprocessor which reads the map data. The navigating unit 16 performsroute guidance for the vehicle on the basis of the retrieved guidanceroute and map data.

The coordinate system definition processor 21 corresponds to acoordinate system definition section, device, or means. As shown in,e.g., FIG. 3, the coordinate system definition processor 21 defines anarbitrary coordinate system B (x,y) on a map which can be displayed onthe basis of the map data, i.e., map including the element polygons Pshowing the constituent elements of the urban map. The coordinate systemB(x,y) is defined irrelevantly to the partitions set in the map data.Note that the present embodiment provides as an example the arbitrarycoordinate system B (x,y) using a “coordinate” having an x coordinateand a y coordinate; thus, a “coordinate” may be also referred to as a“coordinate-set” or a “coordinate-pair.” The accuracy of the coordinatesystem B(x,y) can be adjusted appropriately in accordance with, e.g.,the processing performance of the control unit 11. For example, when theprocessing performance of the control unit 11 is high, a densercoordinate system, i.e., the coordinate system B(x,y) having a largernumber of coordinates can be defined. When the processing performance ofthe control unit 11 is low, a thinner coordinate system, i.e., thecoordinate system B(x,y) having a smaller number of coordinates can bedefined. Note that the coordinates forming the coordinate system B(x,y)are present not only at the intersection points between the grid lines bshown in FIG. 3, but also at many points between the individual gridlines b. The coordinate system B(x,y) may also be defined in associationwith the partitions set in the map data.

The inner and outer coordinate setting processor 22 corresponds to aninner and outer coordinate setting section, device, or means. As shownin FIG. 4, in the coordinate system B, the coordinates located insidethe element polygons P are set as inner coordinates B(1,1) and thecoordinates located outside the element polygons P are set as outercoordinates B(0,0). Note that, in FIG. 4, for the convenience of thedescription, the coordinates set as the inner coordinates B(1,1) areshown by being shaded, while the coordinates set as the outercoordinates B(0,0) are shown without being shaded.

The moving average calculation processor 23 calculates, using apredetermined window width H, a moving average value for each of thecoordinates in the coordinate system B on the basis of, e.g., theexpression (1) or (2) shown in FIG. 5. That is, the moving averagecalculation processor 23 calculates the respective moving average valuesfor the individual coordinates using H coordinate values present aroundeach of the coordinates. In this case, the window width H is set as“2α+1.” The moving average calculation processor 23 specifies the roadhaving a largest road width among the roads D included in the urban mapand sets the road width of the specified road, i.e., the maximum valueof the road widths as a value “α” defining the window width H. That is,the moving average calculation unit 23 sets the window width H on thebasis of the road widths of the roads included in the urban map. Notethat the value “α” may be set, e.g., as an average value of the roadwidths of the roads included in the urban map.

The inner coordinate resetting processor 24 corresponds to an innercoordinate resetting section, device, or means. The inner coordinateresetting processor 24 resets each of the outer coordinates B(0,0) whichhas the moving average value larger than a predetermined value T(0,0) asthe inner coordinate B(1,1). In other words, the inner coordinateresetting processor 24 converts the outer coordinate B(0,0) having themoving average value larger than the predetermined value T(0,0) to theinner coordinate B(0,0). In this case, the window width H is set on thebasis of the maximum value a of the road widths of the roads included inthe urban map and, as the predetermined value T, T(0,0) has been set. Asa result, in FIG. 4, among the outer coordinates B(0,0) present around aregion (hereinafter referred to as “inner region Ru”) formed of anaggregate of the inner coordinates B(1,1), all the coordinates presentwithin the range extending from the outer periphery of the inner regionRu by a distance corresponding to the maximum value a of the road widthshave the moving average values larger than the predetermined valueT(0,0). Accordingly, these outer coordinates B(0,0) are all reset(converted) as/to the inner coordinates B(0,0). Thus, all the outercoordinates B(0,0) present on the roads D shown in FIG. 4 are convertedto the inner coordinates B(1,1) and, as shown in FIG. 6, the innerregion Ru is enlarged by dimensions each corresponding to the maximumvalue a of the road widths.

Then, the inner coordinate resetting processor 24 further resets(converts) each of the outer coordinates B(0,0) surrounded by the innercoordinates B(1,1) as (to) the inner coordinate B(1,1). Thus, the outercoordinate B(0,0) present in, e.g., the region shown by the referencemark c in FIG. 6 is converted to the inner coordinate B(1,1), as shownin FIG. 7. As a result, inside the inner region Ru, the coordinatesB(0,0) and a region (hereinafter referred to as “outer region Rs”)including an aggregate of the outer coordinates B(0,0) no longer exist.Note that, in this case, the region shown by the reference mark ccorresponds to the outer region Rs.

The outer coordinate resetting processor 25 corresponds to an outercoordinate resetting section, device, or means. After the processing bythe inner coordinate resetting processor 24, when there are a pluralityof the inner regions Ru as shown in FIG. 7, the outer coordinateresetting processor 25 resets (converts) each of the inner coordinatesB(1,1) included in each of the plurality of inner regions Ru1 and Ru2which has an area smaller than a predetermined area S as (to) the outercoordinate B(0,0). As a result, e.g., the inner region Ru2 shown in FIG.7, i.e., the inner region having an area smaller than the predeterminedarea S is eliminated, as shown in FIG. 8. On the other hand, the innerregion Ru1 shown in FIG. 7, i.e., the inner region having an area largerthan the predetermined area S is left without being eliminated, as shownin FIG. 8. The predetermined area S can be changed and set appropriatelyin accordance with, e.g., the size of the urban polygon normally assumedor the size of the screen of the display unit 15. Note that theprocessing by the outer coordinate resetting processor 25 may also beset to be performed prior to the processing by the inner coordinateresetting processor 24.

The urban polygon setting processor 26 corresponds to an urban polygonsetting section, device, or means. The urban polygon setting processor26 sets, as a new urban polygon PSnew, a polygon along the outerperiphery of the inner region Ru formed of an aggregate of the innercoordinates B(1,1) that have been set by the inner and outer coordinatesetting processor 22 and the inner coordinate B(1,1) that has been resetby the inner coordinate resetting processor 24. In this case, prior tosetting the new urban polygon, the urban polygon setting processor 26reduces the inner region Ru1 shown in FIG. 8 by dimensions eachcorresponding to the maximum value a of the road widths to provide aninner region Ru11, as shown in FIG. 9. Then, as shown in FIG. 10, theurban polygon setting processor 26 sets, as the new urban polygon PSnew,a polygon along the outer periphery of the reduced inner region Ru11.Note that FIG. 10 virtually shows the element polygons P included in theurban polygon PSnew by the broken lines. The urban polygon PSnew thusset is along the outer periphery of an aggregate of the group of elementpolygons P forming one urban map. Unlike the urban polygon PS, the urbanpolygon PSnew does not include the regions Aα and Aβ where the urban mapshould not be displayed.

The urban map display processor 27 corresponds to an urban map displaysection, device, or means. When the host vehicle location is presentinside the urban polygon PSnew, the urban map display processor 27enables the urban map to be displayed. That is, as shown in, e.g., FIG.11, when the host vehicle location (current location mark M) is presentinside the urban polygon PSnew, the urban map display processor 27displays an urban map display button as a touch button on the screen ofthe display unit 15. Then, when the urban map display button ismanipulated, the map display processor 27 displays the urban map G onthe screen of the display unit 15 on the basis of the element polygons Pincluded in the urban polygon PSnew. On the other hand, when the hostvehicle location is present outside the urban polygon PSnew, the urbanmap display processor 27 disables the urban map from being displayed.That is, the urban map display processor 27 has been configured so asnot to display the urban map display button on the screen of the displayunit 15 when the host vehicle location is present outside the urbanpolygon PSnew.

Next, a description of the content of the urban polygon automaticsetting process performed by the navigation apparatus 10 will be given.

It is noted that a flowchart or the processing of the flowchart in thepresent application includes sections (also referred to as steps), eachof which is represented, for instance, as A1 or B1. Further, eachsection can be divided into several sub-sections while several sectionscan be combined into a single section. Furthermore, each of thusconfigured sections can be also referred to as a processor, device,module, or means. Each or any combination of sections explained in theabove can be achieved as (i) a software section in combination with ahardware unit (e.g., computer) or (ii) a hardware section, including ornot including a function of a related apparatus; furthermore, thehardware section (e.g., integrated circuit, hard-wired logic circuit)may be constructed inside of a microcomputer.

That is, as shown in FIG. 13, on initiating the process, the navigationapparatus 10 newly defines the coordinate system B used for the presentprocess on a map (A1). Then, the navigation apparatus 10 determineswhether or not each of the coordinates in the coordinate system B islocated inside the element polygon P (A2).

When determining that a coordinate is located inside the element polygonP (A2: YES), the navigation apparatus 10 sets the coordinate as theinner coordinate B(1,1) (A3). When determining that a coordinate islocated outside the element polygon P (A2: NO), the navigation apparatus10 sets the coordinate as the outer coordinate B(0,0) (A4).

Next, the navigation apparatus 10 calculates, for each of thecoordinates set as the inner coordinate B(1,1) or the outer coordinateB(0,0), a moving average value using the window width H (2α+1) (A5).Then, the navigation apparatus 10 determines whether or not the movingaverage value of each of the coordinates is larger than thepredetermined value T(0,0) (A6). When determining that the movingaverage value of a coordinate is larger than the predetermined valueT(0,0) (A6: YES), the navigation apparatus 10 sets the coordinate as theinner coordinate B(1,1) (A7). When determining that the moving averagevalue of a coordinate is smaller than the predetermined value T(0,0)(A6: NO), the navigation apparatus 10 sets the coordinate as the outercoordinate B(0,0) (A8). Thus, each of the outer coordinates B(0,0) whichhas the moving average value larger than the predetermined value T(0,0)is reset as the inner coordinate B(1,1). For example, the outercoordinate B(0,0) present on the road D is converted to the innercoordinate B(1,1).

Next, the navigation apparatus 10 determines whether or not each of theremaining outer coordinates B(0,0) is surrounded by the innercoordinates B(1,1) (A9). When determining that an outer coordinateB(0,0) is surrounded by the inner coordinates B(1,1) (A9: YES), thenavigation apparatus 10 resets the outer coordinate B(0,0) as the innercoordinate B(1,1) (A10). When determining that an outer coordinateB(0,0) is not surrounded by the inner coordinates B(1,1) (A9: NO), thenavigation apparatus 10 holds the outer coordinate B(0,0) as the outercoordinate B(0,0) (A11). Thus, the outer region Rs present inside theinner region Ru is eliminated to provide a state where none of the innerregions Ru includes the outer coordinates B(0,0).

Next, when there are the plurality of inner regions Ru, the navigationapparatus 10 determines whether or not the area of each of the innerregions Ru is smaller than the predetermined area S (A12). Then, whendetermining that the area of an inner region Ru is smaller than thepredetermined area S (A12: YES), the navigation apparatus 10 resets eachof the inner coordinates B(1,1) included in the inner region Ru as theouter coordinate B(0,0) (A13). When determining that the area of aninner region Ru is larger than the predetermined area S (A12: NO), thenavigation apparatus 10 holds each of the inner coordinates B(1,1)included in the inner region Ru as the inner coordinate B(1,1) (A14).Thus, the inner region Ru having the area smaller than the predeterminedarea S is eliminated.

Next, the navigation apparatus 10 reduces each of the inner regions Ruremaining without being eliminated by dimensions each corresponding tothe value “α” defining the window width H (A15). Then, the navigationapparatus 10 sets a polygon along the outer periphery of the reducedinner region Ru as the new urban polygon PSnew, i.e., urban polygonwhich does not include a region where the urban map should not bedisplayed (A16).

Next, a description of the content of an urban-map display/non-displaysetting process performed by the navigation apparatus 10 will be given.The process sets the display/non-display of the urban map on the basisof the locational relationship between the host vehicle location and theurban polygon PSnew. That is, as shown in FIG. 14, on detecting thecurrent host vehicle location (B1), the navigation apparatus 10determines whether or not the host vehicle location is present insidethe urban polygon PSnew (B2). When the host vehicle location is presentinside the urban polygon PSnew (B2: YES), the navigation apparatus 10displays, e.g., the urban map display button to enable the urban map tobe displayed (B3). When the host vehicle location is present outside theurban polygon PSnew (B2: NO), the navigation apparatus 10 does notdisplay, e.g., the urban map display button to disable the urban mapfrom being displayed (B4).

The above-described navigation apparatus 10 allows the new urban polygonPSnew to be automatically set on the basis of an aggregated regionformed of an aggregate of the inner coordinates B(1,1) set inside theelement polygons P and coordinates resulting from conversion of theouter coordinates B(0,0) to the inner coordinates B(1,1) based on themoving average value, i.e., the inner region Ru. Since the inner regionRu includes the element polygons P corresponding to the constituentelements of the urban map, the high-precision urban polygon PSnewadequate to the configuration of the urban map can be set on the basisof the inner region Ru. This enables to automatically update the urbanpolygon with high precision without depending on human manipulation.

The navigation apparatus 10 also sets the window width H in the processof calculating the moving average value, i.e., a data number used tocalculate the moving average on the basis of the road widths of theroads included in the urban map. This enables to reliably convert theouter coordinates B(0,0) present on the roads included in the urban mapto the inner coordinates B(1,1) while enabling the resulting innercoordinates B(1,1) to be included in the inner region Ru. This allowseven the road to which the element polygon P has not been set to beincluded in the new urban polygon PSnew.

The navigation apparatus 10 further resets each of the outer coordinatesB(0,0) surrounded by the inner coordinates B(1,1) as the innercoordinate B(1,1). This enables even the outer coordinate B(0,0) presentin the portion of the urban map to which the element polygon has notbeen set, such as a vacant space L, to be converted to the innercoordinate B(1,1) and enables the resulting inner coordinate B(1,1) tobe included in the inner region Ru. Accordingly, even when there is aregion which is to be included in the urban map but to which the elementpolygon P has not been set, the region is enabled to be included in thenew urban polygon PSnew.

The navigation apparatus 10 also reduces each of the inner regions Ru bydimensions each corresponding to the road width a and sets the polygonalong the outer periphery of the reduced region as the new urban polygonPSnew. Accordingly, even when the inner region Ru is enlarged by theprocess of calculating the moving average value, the new urban polygonPSnew can be set on the basis of the inner region Ru in which theenlarged portion has been cancelled out. This enables to generate thehigh-precision urban polygon adequate to the configuration of the urbanmap.

The urban polygon PS shown in FIG. 2 includes the region Aβ by beingaffected by the element polygons P locally present in the region wherethe map data has not been completely prepared. Therefore, the urbanpolygon PS shown in FIG. 2 is inadequate to the configuration of theurban map. In contrast, the navigation apparatus 10 in the presentembodiment is configured as follows. Supposing that a plurality of innerregions Ru are included and a subject inner region Ru of the pluralityof inner regions has an area smaller than the predetermined area S, theinner coordinate B(1,1) included in the subject inner region Ru is resetas the outer coordinate B(0,0). Accordingly, the urban polygon can beprevented from being set on the basis of the inner region Ru having anarea smaller than the predetermined area S. As a result, even when,e.g., the element polygons P are locally present in the region where themap data has not been completely prepared, the urban polygon PSnew canbe generated without being affected by the element polygons P and theregion where the urban map should not be displayed can be prevented frombeing included in the new urban polygon PSnew.

Second Embodiment

A map display system 100 shown in FIG. 15 includes a navigationapparatus 200 and a map data production apparatus 300.

The map data production apparatus 300 produces map data and includes acontrol unit 301 (referred to also as a control circuit 301) controllingthe general operation of the map data production apparatus 300. Thecontrol unit 301 executing a control program virtually implements eachof the coordinate system definition processor 21, the inner and outercoordinate setting processor 22, the moving average calculationprocessor 23, the inner coordinate resetting processor 24, the outercoordinate resetting processor 25, the urban polygon setting processor26, and an urban polygon transmission processor 302, using software.Note that each of these processors 21 to 26 and 302 may also beimplemented as, e.g., an integrated circuit integral with the controlunit 301 using hardware.

The coordinate system definition processor 21, the inner and outercoordinate setting processor 22, the moving average calculationprocessor 23, the inner coordinate resetting processor 24, the outercoordinate resetting processor 25, and the urban polygon settingprocessor 26 are the same as shown in the foregoing embodiment. Astorage unit 304 updatably stores various data such as map data andinformation, similarly to the storage unit 14 in the navigationapparatus 200. The urban polygon transmission processor 302 transmitsthe urban polygon (urban polygon data) set by the urban polygon settingprocessor 26 to the navigation apparatus 200 via a communication unit303. Note that the communication unit 303 is formed of, e.g., a wirelesscommunication module to establish a communication line to the navigationapparatus 200.

The navigation apparatus 200 corresponding to a map display deviceincludes a control unit 201 controlling the general operation of thenavigation apparatus 200. The control unit 201 executing a controlprogram virtually implements an urban polygon acquisition processor 202and the urban map display processor 27, using software. Note that theseprocessors 27 and 202 may also be implemented as, e.g., an integratedcircuit integral with the control unit 201 using hardware.

The urban polygon acquisition processor 202 corresponds to an urbanpolygon acquisition section, device, or means. The urban polygonacquisition processor 202 receives the urban polygon (urban polygondata) transmitted from the map data production apparatus 300 via acommunication unit 203. Thus, the urban polygon acquisition processor202 acquires the urban polygon set by the urban polygon settingprocessor 26 in the map data production apparatus 300. Note that thecommunication unit 203 is formed of, e.g., a wireless communicationmodule to establish a communication line to the map data productionapparatus 300. The urban map display processor 27 is the same as shownin the foregoing embodiment.

The map display system 100 allows the urban polygon to be automaticallyupdated with high precision without depending on human manipulation.That is, the present disclosure may also be configured to perform anurban polygon automatic setting process in an external map dataproduction apparatus to produce map data including the latest urbanpolygon and provide the map data to the map display device. Note thatthe map display device and the map data production apparatus may also beconnected via a wired communication cable.

Other Embodiments

The present disclosure is not limited to each of the above-describedembodiments and is applicable to various embodiments within a range notdeparting from the gist of the present disclosure. For example, thepresent disclosure is applicable not only to a navigation apparatusmounted in a vehicle, but also to a mobile communication terminal havinga navigation function. In this case, the “host vehicle location” may bereplaced appropriately with the current location of the mobilecommunication terminal measured by a location measurement unit includedin the mobile communication terminal. Also, the map display device orthe map display system may be configured appropriately to automaticallyperform the urban polygon automatic setting process every time the mapdata held by the map display device or the map display system isupdated.

It is understood that the present disclosure has been described inaccordance to the examples, but the present disclosure is not limited tothe structure and the embodiment. The present disclosure alsoencompasses variations in the equivalent range as various modifications.In addition, embodiments and various combinations, and further, only oneelement thereof, less or more, and the form and other combinationsincluding, are intended to fall inside the spirit and scope of thepresent disclosure.

The invention claimed is:
 1. A map display device, comprising: acoordinate system definition section that defines a coordinate system ona map including element polygons showing constituent elements of anurban map; an inner and outer coordinate setting section that sets, asinner coordinates, coordinates located inside the element polygons andsets, as outer coordinates, coordinates located outside the elementpolygons; a moving average calculation section that calculates, for eachcoordinate in the coordinate system, a moving average value by using apredetermined window width, wherein the moving average of value for eachcoordinate in the coordinate system is calculated on the basis of one ofthe following expressions; $\begin{matrix}{{B\left( {\overset{\_}{x},\overset{\_}{y}} \right)} = \frac{\sum\limits_{n = {- \alpha}}^{n = {+ \alpha}}\;{\sum\limits_{m = {- \alpha}}^{m = {+ \alpha}}\;{B\left( {{x + m},\;{y + n}} \right)}}}{\left( {{2\alpha} + 1} \right)^{2}}} & (1)\end{matrix}$ $\begin{matrix}{{B\left( {\overset{\_}{x},\overset{\_}{y}} \right)} = \frac{\sum\limits_{n = {- \alpha}}^{n = {+ \alpha}}\;{\sum\limits_{m = {- \alpha}}^{m = {+ \alpha}}{B\left( {{x + m},\;{y + n}} \right)}}}{{2\alpha} + 1}} & (2)\end{matrix}$ wherein B(x,y) is assigned a first predetermined statusvalue when (x,y) is located inside the element polygons, B(x,y) isassigned a second predetermined status value when (x,y) is locatedoutside the element polygons, the value of α is a representative roadwidth, and the value of predetermined window width is 2α+1; an innercoordinate resetting section that resets, as an inner coordinate, eachof the outer coordinates which has the moving average value larger thana predetermined value; an urban polygon setting section that sets, as anurban polygon, a polygon along an outer periphery of a region formed ofan aggregate of the inner coordinates that have been set by the innerand outer coordinate setting section and the inner coordinate that hasbeen reset by the inner coordinate resetting section; and an urban mapdisplay section that enables the urban map to be displayed when acurrent location is present inside the urban polygon.
 2. The map displaydevice according to claim 1, wherein the moving average calculationsection sets the window width based on a road width of a road includedin the urban map.
 3. The map display device according to claim 1,wherein the inner coordinate resetting section further resets, as aninner coordinate, the outer coordinate surrounded by the innercoordinates.
 4. The map display device according to claim 1, wherein theurban polygon setting section reduces the region formed of the aggregateof the inner coordinates by a dimension corresponding to a road widthand sets, as the urban polygon, a polygon along the outer periphery ofthe reduced region.
 5. The map display device according to claim 1,further comprising: an outer coordinate resetting section that resets,when there are a plurality of the regions each formed of the aggregateof the inner coordinates, each of the inner coordinates included in eachof the plurality of regions which has an area smaller than apredetermined area as an outer coordinate.
 6. A map display systemincluding a map display device that displays a map based on map data anda map data preparation apparatus that displays the map data, the mapdata preparation apparatus comprising: a coordinate system definitionsection that defines a coordinate system on a map including elementpolygons showing constituent elements of an urban map; an inner andouter coordinate setting section that sets, as inner coordinates,coordinates located inside the element polygons and sets, as outercoordinates, coordinates located outside the element polygons; a movingaverage calculation section that calculates, for each coordinate in thecoordinate system, a moving average value by using a predeterminedwindow width, wherein the moving average of value for each coordinate inthe coordinate system is calculated on the basis of one of the followingexpressions; $\begin{matrix}{{B\left( {\overset{\_}{x},\overset{\_}{y}} \right)} = \frac{\sum\limits_{n = {- \alpha}}^{n = {+ \alpha}}\;{\sum\limits_{m = {- \alpha}}^{m = {+ \alpha}}{B\left( {{x + m},\;{y + n}} \right)}}}{\left( {{2\alpha} + 1} \right)^{2}}} & (1)\end{matrix}$ $\begin{matrix}{{B\left( {\overset{\_}{x},\overset{\_}{y}} \right)} = \frac{\sum\limits_{n = {- \alpha}}^{n = {+ \alpha}}\;{\sum\limits_{m = {- \alpha}}^{m = {+ \alpha}}{B\left( {{x + m},\;{y + n}} \right)}}}{{2\alpha} + 1}} & (2)\end{matrix}$ wherein B(x,y) is assigned a first predetermined statusvalue when (x,y) is located inside the element polygons, B(x,y) isassigned a second predetermined status value when (x,y) is locatedoutside the element polygons, the value of α is a representative roadwidth, and the value of predetermined window width is 2α+1; an innercoordinate resetting section that resets, as an inner coordinate, eachof the outer coordinates which has the moving average value larger thana predetermined value; and an urban polygon setting section that sets,as an urban polygon, a polygon along an outer periphery of a regionformed of an aggregate of the inner coordinates that have been set bythe inner and outer coordinate setting section and the inner coordinatethat has been reset by the inner coordinate resetting section, the mapdisplay device comprising: an urban polygon acquisition section thatacquires the urban polygon set by the urban polygon setting section; andan urban map display section that enables the urban map to be displayedwhen a current location is present inside the urban polygon.